Resins for crosslinking and adhesion promotion

ABSTRACT

Resins which comprise polymers which contain multiple acetal groups have been developed which are useful for crosslinking and adhesion promotion in coating and adhesive applications. The polymers which make up these resins are prepared by the addition of aminoacetals to polymers containing anhydride functionality. The polymers are modified by titration with ammonia or a primary or secondary amine which solubilizes the polymer in aqueous systems.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation-in-part of U.S. application Ser. No. 08/077,696filed 15 Jun. 1993, now U.S. Pat. No. 5,298,567, the subject matter ofwhich is hereby incorporated by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to alternatives to the use of formaldehydebased crosslinking agents in coating and adhesive applications.

BACKGROUND OF THE INVENTION

Emulsion and solution polymers find wide application as adhesives,binders and coatings. Unfortunately, many of these polymeric materials,especially those prepared predominantly from vinyl acetate, ethylene,vinyl chloride, or their mixtures, show inadequate resistance to waterand other sol vents in their everyday use. In particular, theyexperience substantial and unacceptable loss in strength in the presenceof solvents such as perchloroethylene, methyl ethyl ketone and toluene.In addition, many of these polymers exhibit deficiencies in adhesion tothe substrates on which they are used, for example vinyl acetate,ethylene or vinyl chloride polymers on glass, metal or polyester. Thesedeficiencies are reduced, especially for relatively hydrophilicmonomers, by the use of adhesion promoting or crosslinking comonomersand/or post-added crosslinkers.

Among types of widely used crosslinking materials are aminoplasts,especially N-methylolacrylamide and urea-formaldehyde or melamine-formaldehyde condensates. These materials have met substantial success becausethey are low in cost, highly compatible with aqueous emulsion systems,rapidly cured under acid catalysis, and substrate reactive in that, forexample, they react with the hydroxyl groups of cellulosic materials.These crosslinking materials, however, suffer from two deficiencies: (1)the emission of low levels of formaldehyde during cure and subsequentuse, and (2) inadequate adhesion to certain substrates, for example,metal, glass and polyester.

Many attempts have been made to overcome or minimize the firstdeficiency, especially after the potential carcinogenicity and irritantproperties of formaldehyde became widely recognized.

To reduce the level of formaldehyde in emulsion products, the use ofO-alkylated N-methylolacrylamides such as butoxymethyl acrylamide or theuse of about equimolar ratios of N-methylolacrylamide with acrylamidewere introduced. These materials did not, however, totally eliminate thepresence of formaldehyde.

U.S. Pat. Nos. 4,691,026, 4,663,410, 4,788,288 and 4,864,055 discloseself- and hydroxyl reactive formaldehyde fee cyclic hemiamidal andhemiamide ketal monomers and polymers formed from such monomers. Themonomers can be incorporated into free radical addition polymers whichundergo efficient acid catalyzed, thermally activated post-crosslinkingwith themselves or, alternatively, can react with activehydrogen-containing comonomers of the polymers and/or with groups on thesubstrate to which the polymer is applied. These materials wereadvantageous over prior crosslinking systems in that they provided forgood crosslinking and adhesion promotion without the accompanyingemission of formaldehyde.

SUMMARY OF THE INVENTION

Resins which comprise polymers containing multiple acetal groups havebeen developed which are useful for crosslinking and adhesion promotionin coating and adhesive applications. These resins allow forformaldehyde-free crosslinking which makes them advantageous over theaminoplast systems of the prior art. Additionally, these resins areadvantageous over prior art formaldehyde-free systems in that they arecompatible with water-based coating systems and can be incorporated intothe aqueous phase of an emulsion coating system. The polymers which makeup these resins are prepared by the addition of aminoacetals to polymerscontaining anhydride functionality and can be represented by the generalstructural formula: ##STR1## wherein R¹ is aryl, C₁ -C₂₀ alkyl, C₁ -C₈alkoxy, acetate, halide, or ester; R² is a C₁ -C₆ alkyl group; x is from1 to 6; m is from 0.05 to 0.95; n is from 0.00 to 0.25; and o is from0.10 to 0.80.

Optionally, these polymers may be modified by titration with ammonia ora primary or secondary amine which solubilizes the polymer in aqueoussystems which have been found to be relatively stable at roomtemperature without undergoing uncontrolled, self-crosslinkingreactions.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is a class of resins which are useful forcrosslinking and adhesion promotion in coating and adhesiveapplications. The resins comprise one or more polymers which havemembers represented by the structural formula (I): ##STR2## wherein R¹is aryl, C₁ -C₂₀ alkyl, C₁ -C₈ alkoxy, acetate, halide, or ester; R² isa C₁ -C₆ alkyl group; x is from 1 to 6; m is from 0.05 to 0.95; n isfrom 0.00 to 0.25; and 0 is from 0.10 to 0.80.

These polymers can be prepared by addition of aminoacetals to a polymercontaining anhydride functionality. The degree of amination of thepolymers is controlled by the amount of anhydride present in thepolymer.

The carboxylic acid moiety formed as a result of the amination of theanhydride provides a convenient handle for solubilizing the polymer inaqueous systems by titrating the polymer with a base such as sodiumhydroxide, ammonia, or an amine. For example, the addition of an aminerepresented by the formula (R³)₂ NH wherein each R³ is independently H,C₁ -C₆ alkyl or hydroxyalkyl, or ω,ω-dialkoxyalkyl to the polymer offormula I above affords the corresponding ammonium salt in quantitativeyield. The resulting polymers after complete titration can berepresented by the following structural formula (II): ##STR3##

Maleic anhydride copolymers which have been completely aminated with theaminoacetal (n=0.00) can be titrated with either tertiary amines oralkali bases.

The tertiary amines used for titration can be represented by thestructural formula (R³)₃ N wherein each R³ is independently C₁ -C₆ alkylor hydroxyalkyl. The resultant polymer can be represented by thefollowing structural formula (III): ##STR4##

Alkali bases used for titration are those represented by the chemicalformula M⁺ OH⁻ wherein M⁺ is selected from the group consisting of Li⁺,Na⁺ and K⁺. The polymers, which are optionally completely aminated,which result from titration with these alkali bases can be representedby the structural formula (IV): ##STR5##

Resins comprising these polymers provide for formaldehyde-freecrosslinking systems. Additionally, resins comprising polymersrepresented by structural formulas II, III and IV are compatible withwater-based coating systems and can be incorporated into the aqueousphase of an emulsion coating system. Such aqueous solutions have beenfound to be relatively stable; i.e., 4 to 5 weeks, at room temperaturewithout undergoing uncontrolled, self-crosslinking reactions.

The following examples illustrate this invention and are not intended tolimit its scope.

EXAMPLE 1 Amination of Styrene/Maleic Anhydride Copolymer with4,4-Dimethoxybutylamine

A 30.00 g portion of a styrene/maleic anhydride copolymer (1:1 molarratio of styrene to maleic anhydride; Mw=5,600, Mn=1,800; 0.153 mol ofanhydride functionality) was dissolved in 300 g of tetrahydrofurancontained in a 500 mL round-bottomed flask. With magnetic stirring,20.37 g (0.153 mol) of 4,4-dimethoxybutylamine was added over 30 min.The solution was then heated to reflux for 5 hr. After which time, thesolvent was removed via evaporation under reduced pressure and theresidual yellowish-white product was dried in vacuo (30° C., 0.02 mm Hg)overnight. Infrared spectroscopy of the polymer (KBr pellet) revealed noanhydride functionality in the polymer, but the spectrum possessed aband at 1715 cm⁻¹ (carboxylic acid stretch) and at 1640 cm⁻¹ (amidestretch). The isolated polymer had a mass of 48.40 g and had thecomposition listed in Table 1.

EXAMPLES 2-12 Amination of Styrene/Maleic Anhydride Copolymer with4,4-Dimethoxybutylamine

The procedure described in Example 1 was repeated with styrene/maleicanhydride copolymers of differing composition and molecular weight andwith differing amounts of 4,4-dimethoxybutylamine addition. Infraredspectroscopy of the polymers prepared revealed bands at 1780 cm⁻¹(anhydride stretch), at 1715 cm⁻¹ (carboxylic acid stretch) and at 1640cm⁻¹ (amide stretch) in intensities relative to the respective polymercomposition. The properties of the polymers produced by these proceduresare listed in Table 1.

                                      TABLE 1                                     __________________________________________________________________________    Oligomers Prepared from Amination of Styrene/Maleic Anhydride                 Copolymers with 4,4-Dimethoxybutylamine.                                      Starting   g of    g (mol)                                                    Styrene/   Oligomer                                                                              of 4,4-                                                    Maleic     (mol of Dimethoxy                                                  Example                                                                            Anhydride                                                                           Anhydride                                                                             butyl Isolated                                                                           Composition                                     No.  Oligomer                                                                            Functionality)                                                                        amine Mass (g)                                                                           m  n  o                                         __________________________________________________________________________    1    A     30.00   20.37 48.40                                                                              0.50                                                                             0.00                                                                             0.50                                                 (0.153) (0.153)                                                    2    A     30.00   10.19 39.85                                                                              0.50                                                                             0.25                                                                             0.25                                                 (0.153) (0.0765)                                                   3    A     30.00   5.10  36.57                                                                              0.50                                                                             0.37                                                                             0.13                                                 (0.153) (0.0383)                                                   4    A     30.00   2.04  31.01                                                                              0.50                                                                             0.45                                                                             0.05                                                 (0.153) (0.0153)                                                   5    B     30.00   13.58 42.21                                                                              0.67                                                                             0.00                                                                             0.33                                                 (0.102) (0.102)                                                    6    B     30.00   6.79  36.34                                                                              0.66                                                                             0.17                                                                             0.17                                                 (0.102) (0.0510)                                                   7    B     30.00   3.40  32.73                                                                              0.67                                                                             0.25                                                                             0.08                                                 (0.102) (0.0255)                                                   8    B     30.00   1.36  30.00                                                                              0.67                                                                             0.30                                                                             0.03                                                 (0.102) (0.0102)                                                   9    C     30.00   10.19 39.97                                                                              0.75                                                                             0.00                                                                             0.25                                                 (0.0765)                                                                              (0.0765)                                                   10   C     30.00   5.09  37.21                                                                              0.75                                                                             0.12                                                                             0.12                                                 (0.0765)                                                                              (0.0382)                                                   11   C     30.00   2.54  31.21                                                                              0.75                                                                             0.19                                                                             0.06                                                 (0.0765)                                                                              (0.0191)                                                   12   C     30.00   1.02  31.68                                                                              0.75                                                                             0.23                                                                             0.02                                                 (0.0765)                                                                              (0.0077)                                                   __________________________________________________________________________     Starting oligomers were obtained from Atochem, Inc.:                          (A) SMA1000  1:1 styrene/maleic anhydride molar ratio; Mw = 5,600; Mn =       1,600; Tg = 138° C.                                                    (B) SMA2000  2:1 styrene/maleic anhydride molar ratio; Mw = 7,700; Mn =       1,700; Tg = 124° C.                                                    (C) SMA3000  3:1 styrene/maleic anhydride molar ratio; Mw = 10,300; Mn =      1,900; Tg = 124° C.                                               

EXAMPLES 13-19 Amination of Styrene/Maleic Anhydride Copolymer with4,4-Dimethoxybutylamine

A 150.00 g portion of a styrene/maleic anhydride copolymer (1:1 molarratio of styrene to maleic anhydride; Mw=5,600, Mn=1,800; 0.742 mol ofanhydride functionality) was dissolved in 1500 g of tetrahydrofurancontained in a 2000 mL round-bottomed flask. With magnetic stirring, theamount of 4,4-dimethoxybutylamine shown in Table 2 was added over 30min. The solution was then heated to reflux for 5 hr. After which time,the solvent was removed via evaporation under reduced pressure and theresidual yellowish-white product was dried in vacuo (30° C., 0.02 mm Hg)overnight. Infrared spectroscopy of the polymer (KBr pellet) revealedbands at 1715 cm⁻¹ (carboxylic acid stretch), 1640 cm⁻¹ (amide stretch),and 1780 cm⁻¹ (anhydride stretch), in the intensities indicative of thecompositions listed in Table 2. The composition is that of Formula Iabove, wherein x is 3, R¹ is phenyl and both R² groups are methyl.

                                      TABLE 2                                     __________________________________________________________________________    Oligomers Prepared from Amination of Styrene/Maleic Anhydride                 (SMA) Copolymers with 4,4-Dimethoxybutylamine (ABAA).                              g of Oligomer                                                                 (mol of                                                                       (Anhydride                                                                            g (mol) of                                                                           g of                                                                             Equiv.                                                                              Composition                                      Example                                                                            Functionality)                                                                        (ABAA) THF                                                                              of ABAA                                                                             m  n  o                                          __________________________________________________________________________    13   150 (0.742)                                                                           98.83 (0.742)                                                                        1500                                                                             1.00  0.50                                                                             0.00                                                                             0.50                                       14   150 (0.742)                                                                           84.04 (0.631)                                                                        1500                                                                             0.85  0.50                                                                             0.08                                                                             0.42                                       15   150 (0.742)                                                                           69.12 (0.519)                                                                        1500                                                                             0.70  0.50                                                                             0.15                                                                             0.35                                       16   150 (0.742)                                                                           59.27 (0.445)                                                                        1500                                                                             0.60  0.50                                                                             0.20                                                                             0.30                                       17   150 (0.742)                                                                           49.41 (0.371)                                                                        1500                                                                             0.50  0.50                                                                             0.25                                                                             0.25                                       18   150 (0.742)                                                                           39.56 (0.297)                                                                        1500                                                                             0.40  0.50                                                                             0.30                                                                             0.20                                       19   150 (0.742)                                                                           24.70 (0.185)                                                                        1500                                                                             0.25  0.50                                                                             0.37                                                                             0.13                                       __________________________________________________________________________

EXAMPLE 20 Amination of Methyl Vinyl Ether/Maleic Anhydride Copolymerwith 4,4-Dimethoxybutylamine

A 50.00 g portion of a methyl vinyl ether/maleic anhydride copolymer(1:1 molar ratio of methyl vinyl ether to maleic anhydride; GantrezAN-119; Mw=20,000; 0.3202 mol of anhydride functionality) was aminatedwith 42.65 g (0.3202 mol) of 4,4-dimethoxybutylamine in 1400 mL of THFaccording to the procedure described in Example 1. Infrared spectroscopyof the polymer (KBr pellet) revealed no anhydride functionality in thepolymer, but the spectrum possessed a band at 1730 cm⁻¹ (carboxylic acidstretch) and at 1650 cm⁻¹ (amide stretch). The isolated polymer had amass of 96.06 g.

EXAMPLE 21 Amination of Vinyl Acetate/Maleic Anhydride Copolymer with4,4-Dimethoxybutylamine

A 20.00 g portion of a vinyl acetate/maleic anhydride copolymer(0.9115:0.0885 molar ratio of vinyl acetate to maleic anhydride;Dajac-9184; 0.0204 mol of anhydride functionality) was aminated with2.717 g (0.0204 mol) of 4,4-dimethoxybutylamine in 45 mL of THFaccording to the procedure described in Example 1. Infrared spectroscopyof the polymer (KBr pellet) revealed no anhydride functionality in thepolymer, but the spectrum possessed a band at 1740 cm⁻¹ (carboxylic acidstretch) and at 1650 cm⁻¹ (amide stretch). The isolated polymer had amass of 15.37 g.

EXAMPLE 22 Amination of 1-Octadecene/Maleic Anhydride Copolymer with4,4-Dimethoxybutylamine

A 25.00 g portion of a 1-octadecene/maleic anhydride copolymer (1:1molar ratio of 1-octadecene to maleic anhydride; Chevron PA-18;Mw=35,000; 0.0713 mol of anhydride functionality) was aminated with 9.50g (0.0713 mol) of 4,4-dimethoxybutylamine in 500 mL of THF according tothe procedure described in Example 1. Infrared spectroscopy of thepolymer (KBr pellet) revealed no anhydride functionality in the polymer,but the spectra possessed a band at 1720 cm⁻¹ (carboxylic acid stretch)and at 1640 cm⁻¹ (amide stretch). The isolated polymer had a mass of34.57 g.

EXAMPLE 23 Neutralization of Styrene/N-(4,4-Dimethoxybutyl)maleamic AcidCopolymer with Ammonia

A 25 g portion of a styrene/N-(4,4-dimethoxybutyl)maleamic acidcopolymer from Example 13 was added to an aqueous ammonia solution withvigorous stirring. The mixture was then mildly heated up to a maximum of80° C. until the resin completely dissolved. After which time, thesolution was cooled. This procedure afforded a stable, aqueous solution.This experiment demonstrates that an aqueous solution of these resinscan be slightly acidic without precipitate formation due to prematureacetal hydrolysis and crosslinking.

EXAMPLE 24 Neutralization of Styrene/MaleicAnhydride/N-(4,4-Dimethoxybutyl)maleamic Acid Terpolymer with Ammonia

A 25 g portion of a styrene/maleicanhydride/N-(4,4-dimethoxybutyl)maleamic acid terpolymer was added to anaqueous ammonia solution with vigorous stirring as indicated in Table 4.The mixture was then mildly heated up to a maximum of 80° C. until theresin completely dissolved. After which time, the solution was cooled.This procedure afforded a stable, aqueous solution without precipitateformation due to premature crosslinking. The maleamic acid monomer unitwhich is formed by addition of ammonia to the maleic anhydride monomerunit also provides a site for internal crosslinking with acetalmoieties.

EXAMPLE 25 Neutralization of Styrene/N-(4,4-Dimethoxybutyl)maleamic acidCopolymer with 4,4-Dimethoxybutylamine

A 100 g portion of a styrene/N-(4,4-dimethoxybutyl)maleamic acidcopolymer from Example 13 was added to a solution of4,4-dimethoxybutylamine in water with vigorous stirring. The mixture wasthen mildly heated up to a maximum of 80° C. until the resin completelydissolved, after which time, the solution was cooled. This procedureafforded a stable, aqueous solution without precipitate formation due topremature crosslinking.

EXAMPLE 26 Neutralization of Styrene/N-(4,4-Dimethoxybutyl)maleamic acidCopolymer with Bis(4,4-dimethoxybutyl)amine

A 25 g portion of a styrene/N-(4,4-dimethoxybutyl)maleamic acidcopolymer from Example 13 was added to a solution ofbis(4,4-dimethoxybutyl)amine in water with vigorous stirring. Themixture was then mildly heated up to a maximum of 80° C. until the resincompletely dissolved, after which time, the solution was cooled. Thisprocedure afforded a stable, aqueous solution without precipitateformation due to premature crosslinking.

EXAMPLES 27-34 Reaction of Acetal Containing Oligomers withPentaerythritol

An aqueous suspension of the oligomer prepared in Example 1 wascompletely titrated with 28% aqueous ammonium hydroxide to provide anaqueous solution (30% solids) of the oligomer with 1.00 equivalent ofthe carboxylic acid groups converted to their ammonium salts. Thisaqueous oligomer solution was then combined with aqueous pentaerythritoland para-toluenesulfonic acid monohydrate (p-TSA) according to theamounts presented in Table 3.

                                      TABLE 3                                     __________________________________________________________________________    Composition of Aqueous Solutions of Oligomer, Pentaerythritol, and para-      Toluenesulfonic Acid.                                                                      mmol of                                                                              g of 10%                                                                              mmol of                                           Example                                                                            g of Aqueous                                                                          Acetal Aqueous Hydroxyl                                                                             g of p-                                    No.  Oligomer Sol'n                                                                        Functionality                                                                        Pentaerythritol                                                                       Functionality                                                                        TSA                                        __________________________________________________________________________    27   10.0    8.76   10.0    7.34   --                                         28   10.0    8.76   10.0    7.34   0.10                                       29   10.0    8.76   10.0    7.34   --                                         30   8.67    7.59   8.67    6.37   0.10                                       __________________________________________________________________________

The aqueous solutions of Examples 27 and 28 were maintained at roomtemperature while the aqueous solutions of Examples 29 and 30 weremaintained at 75° C. overnight. After which time, Examples 27 and 28maintained their clear, colorless appearance while Examples 29 and 30were yellowish solutions with the presence of minor amounts ofprecipitate. The solutions of Examples 27 and 28 were then cast as thinfilms on mylar sheets and permitted to air dry overnight. Portions ofeach film were then heated to 100° C. in an air convection ovenovernight. After which, the films were then placed in water (0.25 g offilm in 10 g of water), agitated, and the properties recorded as notedin Table 4.

                                      TABLE 4                                     __________________________________________________________________________    Properties of Untreated and Treated Films.                                                   Film Heat                                                      Example                                                                            Film Prepared                                                                           Treated to                                                                          Film Properties after Re-exposure to                     No.  from Example No.                                                                        100° C.                                                                      Water                                                    __________________________________________________________________________    31   27        no    Dissolved rapidly in water;                                                   afforded a clear colorless                                                    solution.                                                32   27        yes   Very minor solubility in water;                                               yellowish, brittle film.                                 33   28        no    Dissolved rapidly in water;                                                   afforded a clear colorless                                                    solution.                                                34   28        yes   No solubility in water; yellowish,                                            brittle film; no evidence of                                                  swelling.                                                __________________________________________________________________________

Examples 27-34 illustrate that aqueous solutions of the acetalcontaining oligomers can be prepared by base titration of the carboxylicacid moiety, and that these aqueous solutions are relatively stable atroom temperature. At higher temperatures, these solutions begin toundergo acetal exchange reactions in solution. The thermal treatment offilms of these oligomers and pentaerythritol, with or without thepresence of additional acid, also affords acetal exchange reactions.This is reflected in the formation of crosslinks in the oligomer and thelack of water solubility.

EXAMPLE 35 Crosslinking Polyvinyl Alcohol with the Acetal ContainingOligomers

An aqueous suspension of the oligomer prepared in Example 1 waspartially titrated with 28% aqueous ammonium hydroxide to provide anaqueous solution (30% solids) of the oligomer with 0.50 equivalent ofthe carboxylic acid groups converted to their ammonium salts. A 3.27 gportion of the aqueous oligomer solution (2.80 mmol of acetalfunctionality) was added to an aqueous solution of 2.00 g (45.40 mmol ofhydroxyl functionality) of polyvinyl alcohol (Airvol 325, 98-98.8%hydrolyzed, Mw=85,000-146,000) in 18.00 g of water then mixedthoroughly. The resultant aqueous solution was cast as a thin film on amylar sheet and allowed to air dry at room temperature overnight. Thefilm was found to be clear and flexible and readily (20 min) redissolvedin water with minor agitation. A portion of the film was heated in anair oven at 90° C. for 3 hrs. After which time, the heat treated filmwas found to be clear and brittle. After placing in water (100 mg ofheat treated film in 10 g of water) and agitating overnight, the heattreated film swelled but did not dissolve.

This example illustrates the utility of these acetal containingoligomers as crosslinking agents for water-based systems.

EXAMPLE 36 Coatings Utility of ABAA Maleamides Waterborne Coatings

The control formulation was an elevated temperature cure aminocrosslinking system containing Cargill water reducible oil-freepolyester 72-7289 buffered with dimethylethanolamine. Cymel 303 fromAmerican Cyanamid was the hexamethoxymethylmelamine crosslinker. Thisgloss white baking enamel is usually formulated with ˜40% titaniumdioxide pigment, but was made pigment-free for these applicationstudies.

To prepare a nominal 80/20 resin/melamine curative coating, 10.67 gCargill 72-7289 resin, containing 8.00 g of resin solids, was well mixedwith 0.54 g dimethyl ethanol amine, 6.79 g of deionized distilled waterand 2.0 g Cymel 303. For effective wetting, leveling and flow control˜50 mg of 3M's FC-430 FLUORAD fluoroaliphatic polymeric ester was addedand well mixed. The coating formulation was spread onto a 4"×12"22 gaugeunpolished cold-rolled steel test panel which had been wiped down with1/1 methyl ethyl ketone/toluene to remove the last traces of oils. ABird type film applicator with nickel-chrome finish was used to generatea 3" wide by 0.0015" thick wet film. For a final film of ˜1 mil, a 3 mildrawdown bar was used for this 50% solids in water mixture. The platewas allowed to stand 10 minutes in a fume hood, then placed in a vented,forced air convection oven at 350° F. for 10 minutes.

Coatings Physical Property Data

Film hardness by pencil test was done following ASTM D 3363-74. Adhesionby tape test was measured according to ASTM D 3359-87, method B, with 1mm grid spacing. Reverse impact data expressed in inch-pounds weregenerated using method ASTM D 2794-84. The indenter steel punchhemispheric head was 5/8 inch.

Standard Polyester-Melamine Waterborne Coatings

Coating 1 prepared from mixing 10.67 g Cargill 72-7289 polyester resinwith 0.54 g dimethylethanolamine, 6.79 g deionized distilled water and2.00 g Cymel 303 hexamethoxymethylmelamine was tested as noted above;tabulated data summarize critical parameters:

    __________________________________________________________________________    Coat-                                                                             Resin                                                                             Melamine                                                                            Curative                                                                           Solids                                                                            10 min.                                                                             Thickness                                                                           Pencil                                                                             Scratch                                                                            Reverse                          ing %   %     %    %   cure (°F.)                                                                   (mil) Hardness                                                                           Adhesion                                                                           Impact                           __________________________________________________________________________    1   80.0                                                                              20.0  0    50.0                                                                              350   0.95  4H   5    130                              __________________________________________________________________________

Coatings Using Formaldehyde-free Oligomeric Curative

An aqueous suspension of the oligomer prepared in Example 1 was titratedcompletely with triethylamine to provide an aqueous solution (39%solids) of the oligomer with 1.00 equivalent of the carboxylic acidgroups converted to their triethylammonium salts. This was used toreplace hexamethoxymethylmelamine on a 1:1 dry weight solids basis. Atest resin formulation was made with a quarter of the melamine withdrawnand replaced by the styrene maleamide curative; the components were10.67 g Cargill 72-7289 polyester resin with 0.54 gdimethylethanolamine, 6.01 g deionized distilled water, 6.40 g of the30% styrene maleamide oligomer in water and 1.50 g Cymel 303hexamethoxymethylmelamine (Coating 2). Also made was a coating with 50%of the melamine withdrawn and replaced by an equal weight of dialkylacetal amide oligomer (Coating 3).

    __________________________________________________________________________    Coat-                                                                             Resin                                                                             Melamine                                                                            Curative                                                                           Solids                                                                            10 min.                                                                             Thickness                                                                           Pencil                                                                             Scratch                                                                            Reverse                          ing %   %     %    %   cure (°F.)                                                                   (mil) Hardness                                                                           Adhesion                                                                           Impact                           __________________________________________________________________________    2   80.0                                                                              15.0   5.0 50.0                                                                              350   0.90  2H   5    160                              3   80.0                                                                              10.0  10.0 50.0                                                                              350   0.85  2H   5    150                              __________________________________________________________________________

In another series of tests, an aqueous suspension of the oligomerprepared in Example 1 was titrated completely with aqueous ammonia toprovide an aqueous solution (30% solids) of the oligomer with 1.00equivalent of the carboxylic acid groups converted to their ammoniumsalts. Again a control resin formulation was made, approximatelyduplicating the mix ratios of Coating 1, then a total replacement ofmelamine crosslinker was attempted in Coating 5.

    __________________________________________________________________________    Coat-                                                                             Resin                                                                             Melamine                                                                            Curative                                                                           Solids                                                                            10 min.                                                                             Thickness                                                                           Pencil                                                                             Scratch                                                                            Reverse                          ing %   %     %    %   cure (°F.)                                                                   (mil) Hardness                                                                           Adhesion                                                                           Impact                           __________________________________________________________________________    4   80.0                                                                              20.0  0    50.0                                                                              350   1.25  3H   5    170                              5   80.0                                                                              0     20.0 50.0                                                                              350   1.25  2H   4    240                              __________________________________________________________________________

Replacement of hexafunctional melamine with polyfunctionalformaldehyde-free oligomer led to increased reverse impact strength withonly slightly lower hardness and reduced scratch adhesion. This totalreplacement of formaldehyde-generating crosslinker withformaldehyde-free oligomer which is also multifunctional generated,overall, unexpectedly equivalent coating physical properties.

The ability of the styrene maleic anhydride oligomer reacted withaminobutryaldehyde dimethyl acetal and neutralized with ammonia to selfcrosslink was demonstrated by simply drawing down, using ˜50 mg FC-430for 4.0 g of 30% solution, then thermally curing the oligomer (Coating6). The low reverse impact resistance is indicative of a high degree ofbrittleness, consistent with overly efficient crosslinking.

    __________________________________________________________________________    Coat-                                                                             Resin                                                                             Melamine                                                                            Curative                                                                           Solids                                                                            10 min.                                                                             Thickness                                                                           Pencil                                                                             Scratch                                                                            Reverse                          ing %   %     %    %   cure (°F.)                                                                   (mil) Hardness                                                                           Adhesion                                                                           Impact                           __________________________________________________________________________    6   0   0     100  30.0                                                                              350   0.90  3H   3    <1                               __________________________________________________________________________

High Solids Solvent Coatings

Addition products of aminobutyraldehyde dimethyl acetal (ABAA) tostyrene/maleic anhydride (SMA) copolymers dissolved in tetrahydrofurancould be obtained as stable solids by evaporation of the reactionsolvent. The acid amide product could then be redissolved in methoxypropanol acetate at ˜50% solids for formulation with polyester polyolresin to test crosslinkability. In one experiment an SMA/ABAA adductfrom addition of ABAA equivalent to the maleic anhydride content in a75/25 styrene/maleic anhydride resin was mixed in various proportionswith Aroplaz 6755-A6-80 polyester provided by Reichhold Chemicals, Inc.Aroplaz 6755-A6-80 resin is mixed with 13% by weight methoxy propanolacetate (Arcosolv PM acetate, CAS #108-65-6) and 7% by weight toluene(CAS#108-88-3). Dilution with PM acetate solvent allowed film formationstarting at the same solids level for all formulations. No external acidcatalyst was added as the coatings were flash evaporated in a hood afterdrawdown, then cured for 20 minutes at 350° F.

    __________________________________________________________________________    Coat-                                                                             Resin                                                                             SMA/ABAA                                                                             Solids                                                                            Thickness                                                                           Pencil                                                                             Scratch                                                                            MEK double                                 ing wt %                                                                              wt %   (%) (mils)                                                                              Hardness                                                                           Adhesion                                                                           rubs                                       __________________________________________________________________________     7   0  100    33.3                                                                              .80   H    4    >200                                        8  10  90     35.1                                                                              .90   H    5    >200                                        9  20  80     35.1                                                                              .85   H    5     190                                       10  30  70     35.0                                                                              .85   H    5     130                                       11  40  60     35.2                                                                              .80   H    4      50                                       12  50  50     35.0                                                                              .85   H    3      30                                       13  60  40     35.1                                                                              .85   H    2      15                                       14  70  30     35.0                                                                              .85   F    3      10                                       __________________________________________________________________________

The greatest crosslink density, as measured by methyl ethyl ketone (MEK)double rubs, is from self-crosslinking of the SMA/ABAA oligomer,crosslinking induced solely by the oligomer's carboxylic acid groupcatalytic effect, for no external acid such as para-toluenesulfonic acidwas added. Upon dilution with resin the scratch adhesion improves, sothat a balance of property optimization appears to lie between entries 8and 10. With more complete dilution by resin the physical propertybenefits of carboxylic acid-induced crosslinking are reduced due tolimited crosslinking sites in the SMA resin which initially containedonly 25% maleic anhydride.

Having thus described the present invention, what is now deemedappropriate for Letters Patent is set out in the following appendedclaims.

What is claimed is:
 1. A resin useful for crosslinking and adhesionpromotion in coating and adhesive applications which resin comprises apolymer having members of the structural formula: ##STR6## wherein R¹ isaryl, C₁ -C₂₀ alkyl, C₁ -C₈ alkoxy, acetate, halide, or ester; R² is aC₁ -C₆ alkyl group; X is from 1 to 6; m is from 0.05 to 0.95; n is from0.00 to 0.25; and o is from 0.10 to 0.80; which polymer has beentitrated with an amine represented by the chemical formula (R³)₂ NHwherein each R³ is independently H, C₁ -C₆ alkyl or hydroxyalkyl, orω,ω-dialkoxyalkyl.
 2. The resin of claim 1 wherein said resultantpolymer after complete titration has members of the structural formula:##STR7## wherein R¹, R², R³, m, n and o are as set out in claim 1.